AUTHOR'S PREFACE. 



THIS book is an attempt to apply the results of colloid research 

 to biology. The reader may find the undertaking somewhat bold, 

 since the number of facts are so few, and the gaps so numerous that 

 a complete picture is impossible. I find myself somewhat in the 

 position of a palaeontologist who wishes to reconstruct the ancestry 

 of the entire organized world from some chance fragments. Each 

 day brings new finds which must be fitted into his plan and which 

 confirm his views or show that he has been on a false trail. From 

 the nature of things, it happens that I must more often indicate 

 problems than report experimental results. This probably will 

 prove a stimulus to those who wish to take active part in the de- 

 velopment of our young science. 



I wish to state one additional fact: it was not my purpose to 

 make this book exhaustive. I have endeavored to give a general 

 view, and since the work is addressed to biologists and physicians as 

 well as colloid investigators, I have striven to give a clear picture of 

 the subject, disregarding moot questions. On this account the 

 "Introduction to The Study of Colloids" was abbreviated as much as 

 possible without danger of obscuring the subsequent parts. Those 

 who wish to study more thoroughly pure colloid chemistry, I refer 

 to the excellent books of Herbert Freundlich "Kapillarchemie" 

 Leipzig, 1909, and Wolfgang Oswald "Grundris der Kolloidchemie," 

 Dresden. 



Accordingly, in the arrangement of the first part, I have not fol- 

 lowed the usual system, but have been guided by a desire to make 

 easy of comprehension the matters most important to biologists and 

 physicians. On this account I have considered it advisable to de- 

 vote considerable space to the " Methods of Colloid Research." 



Some new unpublished experimental data of my own and some 

 placed at my disposal by others have been included. 



It is finally my privilege to thank all those who have helped me 

 in the preparation of this book, particularly Professors H. Apolant, 

 R. Hober, H. Sachs, and Dr. H. Siedentopf. I am especially in- 

 debted to my dear friend, Professor Richard Lorenz, with whom I 

 have discussed some of the chapters, and to Dr. and Mrs. Ziegler, 



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